Switch mechanism adapted for use in a high-frequency heating system



Jul 11, 1950 c. c. FISHER 2,515,152 SWITCH MECHANISM ADAPTED FOR USE INA HIGH-FREQUENCY HEATING SYSTEM Filed July 16, 1946 K A/ V7]1\\\\\\\\&\\\ 2 INVENTOR CEG/L C. F/SHER Patented July 11, 1950 UNITEDSTAT'ESiiiPATENT (OFFICE SWITCH MECHANISM ADAPTED FOR USE IN AHIGH-FREQUENCY HEATING SYSTEM Cecil. C. Fisher, Lombard, Ill., assignorto Raytheon Manufacturing Company, Newton, Mass., a corporation ofDelaware Application July 16, 1946, Serial No. 684,036

2 Claims.

This invention relates to a switch mechanism,

;' sulating material.

and more particularly to a switch which is adapted for use in ahigh-irequency, high-voltage system.

'An object of this invention is to devise a tem :perature-responsiveswitch adapted for use in a high-frequency heating system.

Another. object is to devise a, thermal switch in which thetemperature-responsive element 1 of said switch is adapted to be placedin a radiofrequency field, without any or the difficulties -ordinarilyexisting when the temperatures of radio-frequency fields are measuredwith con- -:ventional devices.

A further object is to devise a means for measuring temperatures underadverse conditions of high voltage and high frequency.

A still further object is to devise a. temperature simple and thereforeinexpensive.

The foregoing and other objects of the invention will be best understoodfrom the following description. of anexemplification thereof, referencebeinghad to the accompanying drawing, :lwherein the single figure is avertical section through a device embodying the present in- .yvention.

sulating material is fastened to member [3 by means of a threaded shankportion 18 at its upper end. which threadedly engages with a centrally-1 located threaded recess 19 provided in the lower shut-off deviceresponsive to radio-frequency conditions, which device is efiicient-yetrelatively Referring, now, to the drawing, two electrodes .l and 2 areconnected, by means of conductors 33 and 3 to the output terminals 3!and 32 of a high-fr quency oscillator 3, for example, one whose outputis in the radio-frequency range, the dielectric material 4 to be heatedbeing placed between the two electrodes. Electrode 2 is supported by asuitable supporting block 6, for example, of metal, which has anaperture 1 therein. Adjacent the lower face of electrode 2, firmlyattached thereto, and positioned in aperture 1, there is an intermediatepiece or disc 5 of heattransmitting material, for example, of copper. Abimetallic thermal-responsive disc 8 has a central aperature 9, throughwhich a rivet [0 extends in order to firmly fasten the center of saiddisc to the central portion of the bottom surface of piece 5. Acup-shaped member H is positioned centrally of disc 8 and piece 5, saidmember being of such diameter that its upstanding end engages the lowersuriace of disc 8 near its periphery. Aperture 1 is of sufficientdiameter to freely accommodate disc 8, cup H, and piece 5.

Firmly attached to the bottom of cup H, and supporting the same inposition, is a, cylindrical elongated rod l2 of a suitable dielectric orinassembled.

end of member l3. Member i! is provided with a centrally-locatedlongitudinally-extending bore 2B,.which is aligned with bore !4 whenmembers l3 and I! are assembled and which is of sufficient diameter toallow free movement of rod 82 withrespect to member !I, rod [2 extendingthrough bore 20 when members l3 and I! are Member I! has a grommet 2|mounted therein at its lower end for the purpose of guiding rod [2 inits vertical or longi- .tudinal movement.

. Amicroswitch 22, having two electrical terminals 23 and 24, betweenwhich a circuit is made or broken by the operation of said microswitch,is mounted adjacent the lower end of member I l by means of a,supporting framework 25, for

. example of metal, which is in firm engagement with the outer surfaceof the microswitch body or container and which is secured to member I!by mean of a bolt 2t which passes through a transverse aperture inmember ll near the lower end thereof. Microswitch 22 is held in positionin framework 25 by means of a bolt 21 which threadedly engages saidframework and contacts the body or container of said microswitch. Themicroswitch ismounted in such position that the lower end of rod 1 2engages, and is supported by, the actuating button 28 of saidmicroswitch, so that vertical movement of the rod will actuate themicroswitch and, at the same time, the microswitch will support rod l2and cup II in position.

Oscillator 3 is provided with two control terminals 29 and 3t and theseterminals are so connected into the circuit of said oscillator that,when an external circuit between said terminals is interrupted, saidoscillator will be turned off. Terminals 29 and 30 are connected, bymeans of conductors 35 and 36 respectively, to terminals 23 and 24,respectively, of the microswitch, so that, in response to operation ofthe microswitch, oscillator 3 may be turned on or ofi.

The thermal-responsive disc 8, at temperatures below the controltemperature for which it is designed, has a curvature in the directionshown in the drawing, but it is adapted, when said control temperatureis reached, to suddenly reverse its curvature. The temperature of theelectrode 2 is transmitted through piece of heat-conducting material todisc 8. At temperature below the shutofi or control temperature forwhich disc 8 is designed, the elements have the position shown in thedrawing, with microswitch 22 closed and oscillator 3 turned on. When thecontrol temperature is reached by the dielectric material 4 which isbeing heated by radio-frequency energy supplied from oscillator 3, thistemperature is also reached by disc 8, causing said disc to suddenlyreverse its direction of curvature, moving cup II and rod 12 downwardlyto actuate microswitch 22 to its open position, thereby turning offoscillator 3 and stopping the supply of radio-frequency energy tomaterial 4. This switch mechanism therefore acts as a temperatureshutoff device or a temperaturelim iting switch to control the heat in aradiofrequency dielectric heating system.

Since disc 8 operates at a fixed temperature, the device may beconsidered to be a temperature measuring device, because the temperatureof the material 4 is transmitted to the disc 8, where it is measured asbeing above or below the control temperature. It will be noted that noelectrical contact between the radio-frequency electrode and thetemperature-responsive element is required, so that there is nopossibility of arcing to the temperature-responsive element. Since thehigh-voltage portions of the system are electrically insulated, by meansof rod 12 and member I 1 of dielectric material, from the microswitchitself, there is no possibility of the high voltage radiofrequencyenergy interferingwith the operation of the switch mechanism. It willtherefore be seen that I have provided a temperature-responsive switchmechanism which is useful under adverse conditions of high voltage andhigh frequency, and which at the same time is relatively inexpensive.

Of course, it is to be understood that this invention is not limited tothe particular details as described above, as many equivalents willsuggest themselves to those skilled in the art. It is accordinglydesired that the appended claims be given a broad interpretationcommensurate with the scope of this invention within the art.

What is claimed is:

l. A temperature-responsive switch mechanism for use in a high-frequencyelectrical system, comprising a thermal-responsive disc inheatconducting relation with a source of high-frequency electricalenergy the temperature of which is to be measured, a cup-shaped memberin engagement with said disc, an elongated insulating member attached tosaid member, a guiding member of insulating material surrounding saidlast-named member, and a remotely-located microswitch having anactuating element, said microswitch being supported directly from saidguiding member and being so located that said actuating element ismechanically connected to said elongated member.

2. A high frequency electrical system, comprising a pair of electrodesconnected to be supplied with energy from an oscillator, means forsupporting one of said electrodes, said means covering the exteriorsurface of said one electrode but being provided with an aperture whichexposes a portion of the exterior surface of said one electrode, athermal-responsive disc connected at its center to a metallic blockpositioned in said aperture and in heat-conducting relation with saidone electrode, said disc moving in response to heating thereof, aremotely-located switch having an actuating element and a pair ofterminals, insulating means mechanically coupling said disc to saidelement to transmit movements of said disc to said element, and meanselectrically connecting said terminals to said oscillator.

' CECIL C. FISHER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,044,397 Persons June 16, 19362,192,633 Beam Mar. 5, 1940 2,192,852 Hastings Mar. 5, 1940 2,239,540Spencer Apr. 22, 1941 2,386,966 MacMillin Oct. 16, 1945 2,421,098 Vogtet a1 May 27, 1947 2,421,101 Lakso May 27, 1947

